Teen-agers have a tough time in our country, says Elizabeth C. Winship, who should know, since countless adolescents write daily to her as author of the syndicated column "Ask Beth." We cut them out of the mainstream of our lives, give them practically no useful work and leave them to rely on their contemporaries REACHING YOUR TEENAGER. By Elizabeth C. Winship (Houghton Mifflin. 256 pp. Paperback, $7.95) for role models. "It doesn't seem that our society loves them very much," says Winship.

The thorny relationship between teen-agers and their puzzled parents is legendary, and this wise, sensible book, "Reaching Your Teenager," offers much needed common-sense advice. Winship has heard it all: the tormented self-doubts that lead to bitter misunderstandings, the herd instinct that causes the generation gap, the inevitable alienation that so often ends in drugs and unwanted pregnancies. She understands that the changes puberty brings to emotions and behavior cause problems parents find difficult to deal with, and she gives good, hard, specific advice.

There's poignancy in both camps in these uneasy relationships and Winship doesn't miss it. The book is loaded with the cries of adolescents mourning acne, shyness and the trauma of feeling different. You'll have trouble forgetting the parents of Emily, a ninth-grade girl hosting a party for her friends. The blare of the stereo fell silent and, listening from their bedroom, her parents worried. Urged by his wife to investigate, the father protested that he might embarrass their daughter. "Well, you've got to do something," insisted his wife, so reluctantly he went to the head of the stairs and shouted, "Emily, whoop it up a little."

Winship deals with everything from acne to kids hooked on cocaine; her solutions are clear and sympathetic. In good, lively writing devoid of jargon, she offers concrete help. She decrees that 14 to 16 is early enough to date, and minces no words when advising parents to ground kids who break family rules. But she knows that teen-age worries about appearance can be more important to them than a famine in China, and advises parents to take them seriously.

She's especially helpful in her treatment of sex, the subject that generally heads the list of topics most unsuitable for discussion with your mother. I must say her espousal of "The Kinsey Report's" idea of weekly family sex councils seems a little unrealistic, and you have to smile at her suggestion that, if parents feel both they and the kids will be uncomfortable in a sex talk, they write a note. Nevertheless, her discussion of the larger values underlying sex, so often ignored today, is masterly. Her list of questions to ask oneself before deciding on intercourse are so searching many adults might give them some thought.

Winship has filed away not only a lot of adolescent anger but some clever ideas, too. Some of those she passes on make wonderful sense, like the junior high that licked its vandalism problem by promising to give allotted repair money to the students if it wasn't needed. It turned the students into sharp-eyed vigilantes protecting the building.

With divorce so common, the family fragmented and downgraded and a sense of community lost, it's hard to keep kids in line today. Winship makes it clear that parents had better be role models who elicit respect. You can't brag about bilking the IRS and still be surprised and angry when your offspring take up shoplifting. You can't laugh at a friend's overindulgence in liquor and still expect your children to handle drinking sensibly. Above all, you can't be afraid to say no and make it stick. Teen-agers need to test limits, but they need to know they're there.

As the title suggests, Winship believes that communication is the key to surviving the difficult period when your children are learning to break their dependency on you. Wise, loving parents listen and really talk with their children, and speak honestly about touchy matters like money and sex. They should know that a pulling away is normal, and they must be understanding but true to themselves. Inevitably the center of adolescents' lives will move elsewhere and the long job of parenthood will pay off. Give them love and let them go, says Winship. If you did it right, they'll be armed with the trust and self-respect you gave them.